The following description of background art may include insights, discoveries, understandings or disclosures, or associations together with disclosures not known to the relevant art prior to the present disclosure but provided by the present disclosure. Some such contributions of the present disclosure may be specifically pointed out below, while other such contributions of the present disclosure will be apparent from their context.
Color reproduction performance is one of crucial characteristics of a camera, particularly a phone camera, which is incorporated into a mobile phone. The users would always desire the phone camera to capture the object's real color and provide a good color reproduction performance. For many common scenes where rich colors are shown in the images, auto white balance algorithms for the phone camera may obtain good results of the color reproduction. However, for a single color (non-grey) dominant scene, such as a large piece of grass, a blue sky, or single color backgrounds, which takes up a large area of the image, it would be quite challenging for the phone camera to obtain a color reproduction performance as expected.
The commonly used color reproduction algorithms mainly relate to an auto white balance algorithm and other color processing algorithms, such as ‘gray world algorithm’ and ‘white point algorithm,’ which may achieve good color reproduction performance for the scenes or images having rich colors. However, for single color dominant scenes or images without gray or white colors, there are high degrees of difficulties for the white balance algorithms to reproduce the color because no white or grey color could be found as reference points to estimate right illumination and therefore the captured images show chrominance aberration of some levels as compared with the original color.
This single dominant color reproduction problem is also described as ‘gray world failure’ problem in ‘gray world’ white balance algorithm. A technical paper, entitle “Color constancy by characterization of illumination chromaticity,” proposes a method to address this problem by measuring the camera sensor characterization first and then using the estimated illuminance related sensor response Red (“R”), Green (“G”), Blue (“B”) gains to reproduce color. Since the illumination for a single dominant color/gray world failure scene may be erroneously estimated, this method limits the R, G, B gains within Correlated Color Temperature (“CCT”) A to B Kelvin (“K”) to avoid too big gain being applied. In this manner, it may avoid too much chrominance aberration in the single color reproduction. However, it may be incapable of give accurate and tunable results for a single color.
Other solutions to the single dominant color reproduction problem may be based on sensor responses to certain colors in certain illuminations. Some pertinent steps may involve getting a certain single color response under certain illuminances and adjusting the white balance gain according to the color response characterization to achieve the desired color. The problem with this method is that if the single color covers no more than a half area of the image or the single color is not within the pre-calculated scope, the method becomes inefficient and errors would arise in the color reproduction.